Protein-based polymer achieves green electronics

FABIÁN: We have an electronic waste problem. While the development of recyclable plastics has helped curb that problem, currently only about 15% of e-waste is actually recycled. So how can we make a bigger dent? Materials researchers from Denmark are looking to the silkworm for answers.  

ALIREZA DOLATSHAHI-PIROUZ: Who can do it better than Mother Nature, right?

FABIÁN: That’s Prof. Alireza Dolatshahi-Pirouz. His research team at the Technical University of Denmark is developing a new class of thin-film electronics they’ve dubbed “fleco-ionics.” That’s short for flexible, eco-friendly electronics. And they’re doing it using cocoons woven by silkworms. 

DOLATSHAHI-PIROUZ: Silk is one of the strongest materials out there. It has strength that is many times stronger than steel. It’s cheap. It’s readily available in nature. It’s biodegradable. It’s green. It has electronic properties. It is an ionic conductor.

FABIÁN: But silk alone isn’t enough. Films cast from silk fibers are unstable in water. Their unwieldy protein structure, a mixture of random coils and sheets, makes for bad, water-permeable electrodes. To remedy that, a second ingredient is needed, namely, laponite. The nanosized disks that make up this natural ceramic iron out the silk fibers—like pouring hockey pucks on a plate of spaghetti. The result is a water-tight film. And because the disks carry charge of their own, they actually improve the fibers’ ionic conductivity.

DOLATSHAHI-PIROUZ: So it’s pretty amazing, right? You have something that doesn’t work, and then you add something to it, and then suddenly it works. And you get other properties along the way as well. 

FABIÁN: Among the most valuable of those properties are low cost and flexibility. Because although electrodes made of gold, copper, or even carbon nanotubes might show higher conductivity, the team’s silk-nanoclay films are much cheaper and able to wrap around almost any curved surface.

DOLATSHAHI-PIROUZ: That’s not something you typically relate with ordinary electronics. Ordinary electronics are expensive, they are rigid. They consume a lot of power. This does not do that. So that’s why I would say we have something pretty fantastic in our hands at the moment.

FABIÁN: As a proof of concept, the researchers have fashioned the hybrid films into wearable electrodes able to track movement throughout the body, such as the flexing of the elbow or the fiddling of the digits. And that could make for interesting applications down the road.

DOLATSHAHI-PIROUZ: We have plans to use this concept inside a glove to develop an electronic glove. An electronic glove, which I think is the exciting thing about the application right now, would entail to have these small thin films inside a glove, and they would then be connected to an amplifier and a wireless unit that can transmit these signals wirelessly to, let’s say, a computer, or a mobile phone, or a portable device. So you have this glove on your hand that is kind of like sending data to the physician so you can, in real time, monitor whether you’re doing these exercises properly or not.  

FABIÁN: This concept of an e-glove isn’t new. But the approach is. Co-opting natural materials like silk for advanced electronics applications could help cut cost, time, and, perhaps most importantly, the mountains of electronic waste we generate each year. 

DOLATSHAHI-PIROUZ: We need to think simple. Why do we want to do old, complicated chemical syntheses that takes months and years to optimize when we can be smart and look into nature.